Knock codes and hesitation at WOT

[acspecialists]

I've been surfing around and not really finding and answers. I hope someone can save me some pain?

So I have had rich limit codes since I bought the car for both banks. I have done all of the intake gaskets as well as a through inspection and brake cleaner test. After replacing the MAF now I am getting knock codes. I was at the track yesterday and there is also hesitation coming out of the corners at WOT.

Spark plugs are on the way, when I cleaned up the oil during valve cover gasket replacement the plugs looked good so I left them. I also plan on putting in some transmission oil modifier. The fuel filter is new. I plan on chain guides and Vanos rebuild this winter.

[Timm]

If you replaced the MAF (which was quite likely the original problem) with a Chinese copy then you are in for a world of pain until you stick a real BMW OEM one in!

[acspecialists]

Noted, if there is a risk I will change it again. I had so much trouble the first time discovering the problem that I want to check it off as done.

[acspecialists]

If you wouldn't mind I would like to discuss your conclusions?

To be honest I purchased a VW MK4 MAF. I removed the sensor and installed it into my tube. This was based on some research in this forum. While the performance improved significantly it still set the same codes. Then I purchased the actual MAF for my model at more than twice the cost. There was no change in the results so I returned the MAF. Both MAF's were from a local auto parts store. I was heading on a road trip which limited my ability to acquire parts.

So both housings were stamped as Bosch, both sensors were Delpi. I reasoned that the DME map is for the size of the housing and the sensor detects temperature and flow. That being said in my AC business I could buy parts from dealers and discount auto parts stores and get different results. My reasoning is that the manufacturer has a tighter spec and anything that falls outside of that spec is a discount part. All of the parts themselves are from the same place with the same part number and just put in a different package.

So here's the rub, the VW MK4 was $60. The BMW 740 MAF was $180 and the OEM from ECS is $400. Dollars aside it is the same part from the same manufacture. It's not that I don't have the money but come on! I could spend that money on other needs for the car.
Attachment 610200

[Timm]

The VW MAF is not the same as the OEM - but it isn't far enough out to cause knock codes. The curves are different - which means that the mixture can be fine at idle and cruising, but wrong at WOT. You get a loss in performance but not (usually) any error codes or running problems.

Knock codes are usually a result of a mixture that is too lean - rather than too rich. So, something isn't adding up - what were your error codes?

[acspecialists]

The codes are rich limit right bank and left bank. They have been around since I bought the car. I have been chasing vacuum leaks because of these codes. The code is set at part throttle at a 50mph cruise.
After resealing the valley pan and replacing the MAF I have been getting knock codes for sensor 2 & 3. The car was dogging out and eventully would not rev past 3K. Unplugging the MAF caused me to lose the bottom end and gain the top end. Replacing the MAF regained the top and bottom but gained knock codes.

I'm going to throw some plugs spark plugs in the car and then get an OEM MAF. We'll see what happens?

[acspecialists]

Update. Timm is the BMW master!
I was at sea for a month so I haven't followed up. I ordered an OEM MAF for $400. It looks the same as all of the other units but so far the rich limits for bank 1 & 2 have not come back. I'm still getting Knock codes for sensor 3. I have installed new plugs and inspected all of the wiring. Based on my research on the forum most people replace the sensors rather than troubleshoot the cause.

My next idea is to move around some coils and or fuel injectors. A bad coil might fire at the wrong time or a bad fuel injector could lean out a cylinder?